Arctic Skua Vs Great Skua: Key Differences Explained

Arctic Skua Vs Great Skua: Key Differences Explained

Arctic skuas and great skuas often share the same breeding grounds, namely; in Iceland, Norway, the Faroe Islands and the Shetland and Orkney Islands off the north and west coast of Scotland.

This can make differentiating between the two difficult especially when they’re in their breeding grounds. In this article we take a look at the main differences between arctic skuas and great skuas. To find out more, keep reading.

Key Takeaways

At a glance differences between arctic skuas and great skuas include;

  • Arctic skuas are smaller and sleeker than great skuas
  • Great skuas are roughly 20% larger than arctic skuas
  • Great skuas weigh significantly more than arctic skuas (around twice as much)
  • Their eggs are similar in colour and patternation but great skua eggs are significantly larger

What Is The Difference Between Arctic Skuas And Great Skuas?

Let’s look into the main differences between these two fascinating birds. We’ll break it down in the main categories starting with;

Visual Differences

Arctic Skua

At first glance, these two birds look very similar apart from the size difference. They both have a dark plumage with visible white wing flashes.

However, on closer inspection, you will notice that the arctic skua is much smaller and sleeker than the great skua and has a distinctive white eyebrow stripe above each eye.

Great skuas, or Bonxies as they are known in northern Scotland, are around the same size as a herring gull but of a far stockier build. They have large barrel shaped chests which makes them easy to identify. 

Plus they are far darker than even juvenile herring gulls.

Differences In Habitat

This is where things get really confusing because there is no difference in habitat at all. Arctic skuas and great skuas are often found nesting in the same breeding grounds.

They also often steal eggs and young chicks from each other’s nests if they’re left unattended.

Nests & Eggs

The nests of both of these birds are similar in design. They are both shallow depressions in the ground scraped out by the adults and then lined with plant material from the local area. 

The nests are typically located on slight mounds and in direct view of the sea.

The eggs are both similar in colour and design, both being a dark olive/brown with darker brown speckles which helps in keeping them camouflaged from above as they blend into the surrounding landscape.

However, it’s the size that differentiates the two. 

Arctic skua eggs are around 58 x 40 mm in size and weigh around 48 grams.

Great skua eggs are around 70 x 50 mm in size and weigh around 91 grams.

Bird Calls

Great Skua

It is generally easy to distinguish between great skuas and arctic skuas purely by their bird calls. 

Great skuas make a harsh “hah-hah, hah-hah” sound along with other croaking or quacking sounds. However, they are relatively quiet when out at sea.

Arctic skuas make a more nasal mewing type sound typically during their aerial displays when intimidating other birds for food. They can also make a shrill alarm-like sound when they feel threatened.

Both of these birds use their calls as part of their social interaction and in order to claim their territory.

Size & Weight

These two bird species vary in both size and weight which can make it easy to differentiate between the two if seen side by side.

Differences In Size

Arctic skuas are around 40 to 45 cm long with a wingspan of between 110 to 125 cm. 

Great skuas are around 53 to 58 cm long with a wingspan of between 125 to 140 cm.

So overall, the great skua is considerably larger than the arctic skua and typically has a longer wingspan as well. This can be confusing when there are juvenile birds of each species present.

But once they become fully grown the differences are quite obvious.

Differences In Weight

Due to the differences in size, the weights of these two species are another easy way to distinguish between the two.

Great skuas weigh around 1.2 to 2 kg which is considerably more than arctic skuas which weigh in at around 330 to 570 g. Less than ½ the weight of the great skua.

SEE ALSO: Blue Tit vs Great Tit: Key Differences Explained

Frequently Asked Questions

What are great skuas known as in Scotland?

Great skuas are known as “Bonxies” in Scotland. This is thought to be derived from an old norse word meaning “dumpy” and refers to the shape and size of the bird.

How can I tell the difference between the great skua and arctic skua?

Great skuas are far larger, heavier and bulkier than arctic skuas plus arctic skuas have a white stripe above each eye.

What are the biggest threats to the great skua?

In recent times, the biggest threat to the great skua is avian flu. Followed by the reduction in the sand eel population off the Scottish coast.

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